30sec hangup on changing task?!

30sec hangup on changing task?!

The program works fine and downloads at full speed while it is in the background or while it is in the foreground. Just when i try to change the task (e.g. after telling the program which file to copy, I change the task to firefox to browse the net) my computer hangs up for like 30sec just to recover again.
This works both way (WinSCP --> other task or other task --> WinSCP) but does not interfere with the file transfer. Any ideas why this could be?

Ok, I deinstalled ZoneAlarm (it started to piss me off) thus fixing my firewall problem. And now my computer doesn't hangup each time i change the task anymore! Must have been a problem with zonealarm, thanks anyways for your interest in fixing this :-)